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    <div id="projectbrief">A high quality OpenGL text rendering engine for C</div>
    
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   &#160;<span id="projectnumber">0.1</span>
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   <div id="projectbrief">A high quality OpenGL text rendering engine for C</div>
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<div class="title">edtaa3func.h</div>  </div>
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<div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/*</span>
<a name="l00002"></a>00002 <span class="comment"> * Copyright 2009 Stefan Gustavson (stefan.gustavson@gmail.com)</span>
<a name="l00003"></a>00003 <span class="comment"> * All rights reserved.</span>
<a name="l00004"></a>00004 <span class="comment"> *</span>
<a name="l00005"></a>00005 <span class="comment"> * Redistribution and use in source and binary forms, with or without</span>
<a name="l00006"></a>00006 <span class="comment"> * modification, are permitted provided that the following conditions are met:</span>
<a name="l00007"></a>00007 <span class="comment"> *</span>
<a name="l00008"></a>00008 <span class="comment"> *  1. Redistributions of source code must retain the above copyright notice,</span>
<a name="l00009"></a>00009 <span class="comment"> *     this list of conditions and the following disclaimer.</span>
<a name="l00010"></a>00010 <span class="comment"> *</span>
<a name="l00011"></a>00011 <span class="comment"> *  2. Redistributions in binary form must reproduce the above copyright</span>
<a name="l00012"></a>00012 <span class="comment"> *     notice, this list of conditions and the following disclaimer in the</span>
<a name="l00013"></a>00013 <span class="comment"> *     documentation and/or other materials provided with the distribution.</span>
<a name="l00014"></a>00014 <span class="comment"> *</span>
<a name="l00015"></a>00015 <span class="comment"> * THIS SOFTWARE IS PROVIDED BY STEFAN GUSTAVSON &#39;&#39;AS IS&#39;&#39; AND ANY EXPRESS OR</span>
<a name="l00016"></a>00016 <span class="comment"> * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF</span>
<a name="l00017"></a>00017 <span class="comment"> * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO</span>
<a name="l00018"></a>00018 <span class="comment"> * EVENT SHALL STEFAN GUSTAVSON OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,</span>
<a name="l00019"></a>00019 <span class="comment"> * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES</span>
<a name="l00020"></a>00020 <span class="comment"> * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;</span>
<a name="l00021"></a>00021 <span class="comment"> * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND</span>
<a name="l00022"></a>00022 <span class="comment"> * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT</span>
<a name="l00023"></a>00023 <span class="comment"> * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF</span>
<a name="l00024"></a>00024 <span class="comment"> * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.</span>
<a name="l00025"></a>00025 <span class="comment"> *</span>
<a name="l00026"></a>00026 <span class="comment"> * The views and conclusions contained in the software and documentation are</span>
<a name="l00027"></a>00027 <span class="comment"> * those of the authors and should not be interpreted as representing official</span>
<a name="l00028"></a>00028 <span class="comment"> * policies, either expressed or implied, of Stefan Gustavson.</span>
<a name="l00029"></a>00029 <span class="comment"> *</span>
<a name="l00030"></a>00030 <span class="comment"> *</span>
<a name="l00031"></a>00031 <span class="comment"> * edtaa3()</span>
<a name="l00032"></a>00032 <span class="comment"> *</span>
<a name="l00033"></a>00033 <span class="comment"> * Sweep-and-update Euclidean distance transform of an</span>
<a name="l00034"></a>00034 <span class="comment"> * image. Positive pixels are treated as object pixels,</span>
<a name="l00035"></a>00035 <span class="comment"> * zero or negative pixels are treated as background.</span>
<a name="l00036"></a>00036 <span class="comment"> * An attempt is made to treat antialiased edges correctly.</span>
<a name="l00037"></a>00037 <span class="comment"> * The input image must have pixels in the range [0,1],</span>
<a name="l00038"></a>00038 <span class="comment"> * and the antialiased image should be a box-filter</span>
<a name="l00039"></a>00039 <span class="comment"> * sampling of the ideal, crisp edge.</span>
<a name="l00040"></a>00040 <span class="comment"> * If the antialias region is more than 1 pixel wide,</span>
<a name="l00041"></a>00041 <span class="comment"> * the result from this transform will be inaccurate.</span>
<a name="l00042"></a>00042 <span class="comment"> *</span>
<a name="l00043"></a>00043 <span class="comment"> * By Stefan Gustavson (stefan.gustavson@gmail.com).</span>
<a name="l00044"></a>00044 <span class="comment"> *</span>
<a name="l00045"></a>00045 <span class="comment"> * Originally written in 1994, based on a verbal</span>
<a name="l00046"></a>00046 <span class="comment"> * description of the SSED8 algorithm published in the</span>
<a name="l00047"></a>00047 <span class="comment"> * PhD dissertation of Ingemar Ragnemalm. This is his</span>
<a name="l00048"></a>00048 <span class="comment"> * algorithm, I only implemented it in C.</span>
<a name="l00049"></a>00049 <span class="comment"> *</span>
<a name="l00050"></a>00050 <span class="comment"> * Updated in 2004 to treat border pixels correctly,</span>
<a name="l00051"></a>00051 <span class="comment"> * and cleaned up the code to improve readability.</span>
<a name="l00052"></a>00052 <span class="comment"> *</span>
<a name="l00053"></a>00053 <span class="comment"> * Updated in 2009 to handle anti-aliased edges.</span>
<a name="l00054"></a>00054 <span class="comment"> *</span>
<a name="l00055"></a>00055 <span class="comment"> * Updated in 2011 to avoid a corner case infinite loop.</span>
<a name="l00056"></a>00056 <span class="comment"> *</span>
<a name="l00057"></a>00057 <span class="comment"> */</span>
<a name="l00058"></a>00058 <span class="preprocessor">#ifndef __EDTAA3FUNC_H__</span>
<a name="l00059"></a>00059 <span class="preprocessor"></span><span class="preprocessor">#define __EDTAA3FUNC_H__</span>
<a name="l00060"></a>00060 <span class="preprocessor"></span>
<a name="l00061"></a>00061 <span class="preprocessor">#ifdef __cplusplus</span>
<a name="l00062"></a>00062 <span class="preprocessor"></span><span class="keyword">extern</span> <span class="stringliteral">&quot;C&quot;</span> {
<a name="l00063"></a>00063 <span class="preprocessor">#endif</span>
<a name="l00064"></a>00064 <span class="preprocessor"></span>
<a name="l00065"></a>00065 
<a name="l00066"></a>00066 <span class="preprocessor">#include &lt;math.h&gt;</span>
<a name="l00067"></a>00067 
<a name="l00068"></a>00068 
<a name="l00069"></a>00069 <span class="comment">/*</span>
<a name="l00070"></a>00070 <span class="comment"> * Compute the local gradient at edge pixels using convolution filters.</span>
<a name="l00071"></a>00071 <span class="comment"> * The gradient is computed only at edge pixels. At other places in the</span>
<a name="l00072"></a>00072 <span class="comment"> * image, it is never used, and it&#39;s mostly zero anyway.</span>
<a name="l00073"></a>00073 <span class="comment"> */</span>
<a name="l00074"></a>00074 <span class="keywordtype">void</span> computegradient(<span class="keywordtype">double</span> *img, <span class="keywordtype">int</span> w, <span class="keywordtype">int</span> h, <span class="keywordtype">double</span> *gx, <span class="keywordtype">double</span> *gy);
<a name="l00075"></a>00075 
<a name="l00076"></a>00076 <span class="comment">/*</span>
<a name="l00077"></a>00077 <span class="comment"> * A somewhat tricky function to approximate the distance to an edge in a</span>
<a name="l00078"></a>00078 <span class="comment"> * certain pixel, with consideration to either the local gradient (gx,gy)</span>
<a name="l00079"></a>00079 <span class="comment"> * or the direction to the pixel (dx,dy) and the pixel greyscale value a.</span>
<a name="l00080"></a>00080 <span class="comment"> * The latter alternative, using (dx,dy), is the metric used by edtaa2().</span>
<a name="l00081"></a>00081 <span class="comment"> * Using a local estimate of the edge gradient (gx,gy) yields much better</span>
<a name="l00082"></a>00082 <span class="comment"> * accuracy at and near edges, and reduces the error even at distant pixels</span>
<a name="l00083"></a>00083 <span class="comment"> * provided that the gradient direction is accurately estimated.</span>
<a name="l00084"></a>00084 <span class="comment"> */</span>
<a name="l00085"></a>00085 <span class="keywordtype">double</span> edgedf(<span class="keywordtype">double</span> gx, <span class="keywordtype">double</span> gy, <span class="keywordtype">double</span> a);
<a name="l00086"></a>00086 
<a name="l00087"></a>00087 
<a name="l00088"></a>00088 <span class="keywordtype">double</span> distaa3(<span class="keywordtype">double</span> *img, <span class="keywordtype">double</span> *gximg, <span class="keywordtype">double</span> *gyimg, <span class="keywordtype">int</span> w, <span class="keywordtype">int</span> c, <span class="keywordtype">int</span> xc, <span class="keywordtype">int</span> yc, <span class="keywordtype">int</span> xi, <span class="keywordtype">int</span> yi);
<a name="l00089"></a>00089 
<a name="l00090"></a>00090 <span class="comment">// Shorthand macro: add ubiquitous parameters dist, gx, gy, img and w and call distaa3()</span>
<a name="l00091"></a>00091 <span class="preprocessor">#define DISTAA(c,xc,yc,xi,yi) (distaa3(img, gx, gy, w, c, xc, yc, xi, yi))</span>
<a name="l00092"></a>00092 <span class="preprocessor"></span>
<a name="l00093"></a>00093 <span class="keywordtype">void</span> edtaa3(<span class="keywordtype">double</span> *img, <span class="keywordtype">double</span> *gx, <span class="keywordtype">double</span> *gy, <span class="keywordtype">int</span> w, <span class="keywordtype">int</span> h, <span class="keywordtype">short</span> *distx, <span class="keywordtype">short</span> *disty, <span class="keywordtype">double</span> *dist);
<a name="l00094"></a>00094 
<a name="l00095"></a>00095 
<a name="l00096"></a>00096 <span class="preprocessor">#ifdef __cplusplus</span>
<a name="l00097"></a>00097 <span class="preprocessor"></span>}
<a name="l00098"></a>00098 <span class="preprocessor">#endif</span>
<a name="l00099"></a>00099 <span class="preprocessor"></span>
<a name="l00100"></a>00100 <span class="preprocessor">#endif // __EDTAA3FUNC_H__</span>
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